1. Field of the Invention
The present invention relates generally to optical devices, and more particularly, but not exclusively, to devices employed in optical signal transmission.
2. Description of the Background Art
Light is an electromagnetic wave. As such, light has a corresponding electric field vector that can be resolved into two orthogonal polarization states, such as a “P-component” and an “S-component” with respect to a reference surface. Light may also be polarized such that it only has one component. Light that only has a P-component is known as “P-polarized”, while light that only has an S-component is known as “S-polarized”.
Polarization-dependent loss refers to the sensitivity of an optical device to the polarization state of an input signal, such as a light beam. An optical device with relatively high polarization-dependent loss would exhibit varying losses depending on the polarization state of the input signal. That is, the optical device may have one loss value for the S-component of the input signal and another loss value for the P-component of the input signal. In telecommunications applications where input signals typically have polarization states that fluctuate randomly, polarization-dependent loss may result in variations of the output signal levels, for example. That is, polarization state fluctuations may produce magnitude fluctuations that can be mistaken as data and give rise to bit-errors.
From the foregoing, a technique for mitigating the effects of polarization-dependent loss in optical devices is highly desirable.